In prestressed reinforced concrete form construction, a significant limiting factor is the weight of the concrete forms and their translation into transportation costs. For this reason large pre-cast concrete forms, such as those comprising a substantial part of a wall or a floor, rarely can be justified at distances beyond 250 to 300 miles from their source. Larger concrete forms therefore tend to be poured in place at the construction site. Pre-cast, prestressed concrete forms have advantages over concrete poured in place.
The initial tension in the steel rods is translated into internal compression in the concrete. Therefore, there are no cracks in the concrete slab due to expansion and contraction caused by temperature changes, and the member can be thinner, saving material.
However, another limiting factor is the combined cost of the equipment needed to pre-cast and reinforce the concrete forms and the cranes needed to raise them to vertical orientation at the construction site and to move them into place. Thereafter other equipment is needed to brace and anchor the concrete forms in position during the course of construction. The problem is intensified when a multiple of pre-casting molds are needed to cast multiple shapes for walls and floors of structure under construction.
Hence, the purpose of this invention is to overcome the cost disadvantages associated with pre-cast, prestressed concrete construction by reducing significantly the labor costs, equipment costs, transportation costs and other costs associated with slow methods of construction with concrete.
Another purpose of the invention is to provide the means for multiple pre-casting of concrete forms at the site.
Another purpose is to provide a single, or limited number of pre-cast concrete forms that can be used for walls, floor and roof.
Another purpose is to provide the means for pre-casting the multi-purpose concrete form at site, thus combining the economics of on-site fabrication and multi-use in one embodiment.
A further purpose of the invention is to provide a means for pre-stressing pre-cast concrete forms with reinforcing rods in both a longitudinal and a transverse direction.